1. Technical Field of the Invention
This invention relates generally to optical elements and methods for treating optical elements.
2. Description of the Related Art
As is known, some optical imaging systems include one or more externally mounted optical elements that shield the remainder of the imaging system from an external environment. For example, with infrared (IR) airborne imaging systems, an IR transparent optical element, such as a window or dome, may be part of the airborne system, used to isolate the remainder of the imaging system from exposure to humid, corrosive, and abrasive environments. Such elements often find applications on missiles, for example as part of a radar dome for a missile.
Zinc sulfide has been used in the past as a material for such domes. These materials are capable of providing a degree of mechanical durability and of providing reasonable optical performance in the long infrared imaging wavelength band of approximately 8-12 microns.
Chemically-vapor-deposited zinc sulfide has been treated in order to improve optical properties of the material for visible and near-infrared wavelengths, for example by changing the chemically-vapor-deposited zinc sulfide to multispectral zinc sulfide. One way of doing so has been to bring platinum into contact with the zinc sulfide or zinc selenide, and then heat the combination under pressure in a hot isostatic pressure (HIP) treatment. Such a treatment is described in U.S. Pat. No. 4,944,900.
However platinum is an expensive material, making the treatment costly. There is thus room for improvement with regard to such optical materials and their treatment.